Calculation of integrated circuit timing delay using frequency domain

Abstract

Accurate circuit and system timing analysis is a critical tool for designing and analyzing complex modern semiconductor chips. While the accuracy and detail of dynamic electrical simulation may be desirable in theory, such analysis is not feasible due to extreme computational complexity and open-ended simulation times. Improved circuit modeling and timing analysis tools that can provide both accuracy and computational efficiency are required. Table look-up (TLU) and other techniques provide computationally efficient timing analysis but may be undertaken at the expense of simulation accuracy. Instead, the use of current waveform moments representing the frequency domain equivalents of signals can provide the required simulation accuracy and computational efficiency.

What is claimed is: 
     
       1. A computer implemented method for delay calculation comprising:
 obtaining, using one or more processors, an input voltage waveform to a circuit wherein the input voltage waveform comprises an input slew and wherein the circuit comprises a driver circuit with an output connected to a wiring circuit wherein the wiring circuit has one or more sinks; 
 pre-processing a composite current source library, wherein the library includes a representation of the driver circuit; 
 determining current waveform moments for the driver circuit based on the pre-processing, the input slew to the driver circuit, and the wiring circuit which is connected to the output of the driver circuit; 
 convolving the current waveform moments for the driver circuit with a frequency domain impulse response function for the wiring circuit to produce a frequency domain function for a voltage waveform at each sink; and 
 calculating a delay and slew to each sink of the circuit based on the frequency domain function for the voltage waveform at each sink, where the input voltage waveform further comprises an input delay. 
 
     
     
       2. The method of  claim 1  wherein the delay is based on the input delay. 
     
     
       3. The method of  claim 1  wherein the calculating the delay and slew is calculated using poles and residues for each sink. 
     
     
       4. The method of  claim 3  wherein the poles and residues are computed using a Newton-Raphson method. 
     
     
       5. The method of  claim 1  wherein the pre-processing includes generation of a vector of current waveform moments based on input slews and effective capacitances. 
     
     
       6. The method of  claim 1  wherein the current waveform moments for the driver circuit, which were obtained, are based on an effective capacitance of the wiring circuit. 
     
     
       7. The method of  claim 6  wherein the effective capacitance is based on distributive capacitive load in the wiring circuit. 
     
     
       8. The method of  claim 7  wherein the effective capacitance is further based on the current waveform moments for the driver circuit. 
     
     
       9. The method of  claim 8  further comprising iterating between the current waveform moments and the effective capacitance. 
     
     
       10. The method of  claim 1  further comprising computing a voltage waveform at each sink. 
     
     
       11. The method of  claim 1  wherein one of the sinks is connected to a receiver circuit. 
     
     
       12. The method of  claim 1  wherein the composite current source library includes a table for look up of circuit moments. 
     
     
       13. The method of  claim 1  further comprising using a look-up table to perform one of a group comprising static timing analysis, statistical timing analysis, noise computation, and static noise analysis. 
     
     
       14. A computer program product embodied in a non-transitory computer readable medium for delay calculation, the computer program product comprising:
 code for obtaining an input voltage waveform to a circuit wherein the input voltage waveform comprises an input slew and wherein the circuit comprises a driver circuit with an output connected to a wiring circuit wherein the wiring circuit has one or more sinks; 
 code for pre-processing a composite current source library, wherein the library includes a representation of the driver circuit; 
 code for, determining current waveform moments for the driver circuit based on the pre-processing, the input slew to the driver circuit, and based on the wiring circuit which is connected to the output of the driver circuit; 
 code for convolving the current waveform moments for the driver circuit with a frequency domain impulse response function for the wiring circuit to produce a frequency domain function for a voltage waveform at each sink; and 
 code for calculating a delay and slew to each sink of the circuit based on the frequency domain function for the voltage waveform at each sink, where the input voltage waveform further comprises an input delay. 
 
     
     
       15. The computer program product of  claim 14  wherein the pre-processing includes generation of a vector of current waveform moments based on input slews and effective capacitances. 
     
     
       16. A computer system for delay calculation comprising:
 a memory for storing instructions; 
 one or more processors connected to the memory wherein the one or more processors are configured to:
 obtain an input voltage waveform to a circuit wherein the input voltage waveform comprises an input slew and wherein the circuit comprises a driver circuit with an output connected to a wiring circuit wherein the wiring circuit has one or more sinks; 
 pre-process a composite current source library, wherein the library includes a representation of the driver circuit; 
 determine current waveform moments for the driver circuit based on the pre-processing, the input slew to the driver circuit, and the wiring circuit which is connected to the output of the driver circuit; 
 convolve the current waveform moments for the driver circuit with a frequency domain impulse response function for the wiring circuit to produce a frequency domain function for a voltage waveform at each sink; and 
 calculate a delay and slew to each sink of the circuit based on the frequency domain function for the voltage waveform at each sink, where the input voltage waveform further comprises an input delay. 
 
 
     
     
       17. The system of  claim 16  wherein pre-processing includes generation of a vector of current waveform moments based on input slews and effective capacitances.